Cardiac retractor

ABSTRACT

A cardiac retractor is disclosed. The cardiac retractor has an outer tube. The cardiac retractor also has a fixed collar fixedly coupled to a proximal end of the outer tube. The cardiac retractor further has a fixed link fixedly coupled to a distal end of the outer tube. The cardiac retractor also has an inner tube rotatable within the outer tube. The cardiac retractor further has a fixed key coupled to a proximal end of the inner tube and configured to rotate the inner tube relative to the outer tube. The cardiac retractor also has a keyed link coupled to a distal end of the outer tube.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application No. 63/066,376, filed Aug. 17, 2020 and entitled “CARDIAC RETRACTOR,” the contents of which is hereby incorporated by reference in its entirety. In addition, this application is a continuation-in-part of U.S. patent application Ser. No. 17/351,332, filed Jun. 18, 2021 and entitled “CARDIAC RETRACTOR,” which is a continuation of U.S. patent application Ser. No. 16/407,171, filed May 8, 2019 and entitled “CARDIAC RETRACTOR,” which claims priority to U.S. Provisional Patent Application No. 62/668,751, filed May 8, 2018 and entitled “CARDIAC RETRACTOR,” the contents of each of which is hereby incorporated by reference in its entirety.

FIELD

The claimed invention relates to surgical retractors, and more specifically to surgical retractors for use in minimally invasive cardiac surgery.

BACKGROUND

Modern advances in cardiac surgery have made it possible to repair or replace heart valves using minimally invasive surgical techniques. As minimally invasive techniques have improved, surgeons are able to operate on patients through smaller and smaller access incisions, resulting in less perioperative pain and shorter recovery times. Unfortunately, many cardiac retractors used in maintaining an opening in the wall of the heart require more than one access incision when used in minimally invasive surgery: one incision for the majority of the retractor to be passed through, and a second incision through which a manipulator/stabilizer is inserted to be coupled to the retractor to keep the retractor aligned as desired.

It would be desirable to have a reliable, simple to use cardiac retractor for use in minimally invasive surgery which could be deployed through a single minimally invasive incision/opening.

SUMMARY

A cardiac retractor is disclosed. The cardiac retractor has an outer tube. The cardiac retractor also has a fixed collar fixedly coupled to a proximal end of the outer tube. The cardiac retractor further has a fixed link fixedly coupled to a distal end of the outer tube. The cardiac retractor also has an inner tube rotatable within the outer tube. The cardiac retractor further has a fixed key coupled to a proximal end of the inner tube and configured to rotate the inner tube relative to the outer tube. The cardiac retractor also has a keyed link coupled to a distal end of the outer tube.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of a cardiac retractor.

FIGS. 2A-2H and 2J are a series of exploded perspective views which illustrate the partial assembly of the cardiac retractor of FIG. 1. It should be noted that there is intentionally not a FIG. 2I to avoid confusion with the number 21.

FIG. 2K is a schematic elevational view of an embodiment of the deployment cable routing for the assembly of the cardiac retractor of FIG. 1.

FIGS. 2L-2N are a continued series of exploded perspective views which illustrate the remaining assembly of the cardiac retractor of FIG. 1.

FIG. 3A is a top view of the cardiac retractor of FIG. 1 showing cross-section line 3B-3B.

FIG. 3B is a side cross-sectional view of the cardiac retractor of FIG. 3A.

FIG. 4 is a perspective view of one embodiment of a keyhole cannula for use with a cardiac retractor such as the retractor of FIG. 1.

FIGS. 5A, 5B, 5C, 5D, 5E, and 5F are front, left, right, back, top, and bottom views, respectively, of the keyhole cannula of FIG. 4.

FIGS. 6A-6H, 6J-6N, and 6P-6R illustrate an example of a surgical procedure using the cardiac retractor of FIG. 1 and the keyhole cannula of FIG. 4.

FIG. 7 is a perspective view of another embodiment of a cardiac retractor.

FIG. 8A is a top view of the cardiac retractor of FIG. 7 showing cross-section line 8B-8B.

FIG. 8B is a side cross-sectional view of the cardiac retractor of FIG. 8A.

FIGS. 9A and 9B are both partial cross-sectional and partially exposed views which illustrate the deployment cable mechanism for the cardiac retractor embodiment of FIG. 7.

FIG. 10 is a perspective view of a distal end of another embodiment of a cardiac retractor.

FIGS. 11A-11C are schematic elevational views of the distal end of the cardiac retractor of FIG. 10 illustrating various states of deployment of the cardiac retractor.

FIGS. 12A-12B are schematic elevational views of the distal end of another embodiment of a cardiac retractor.

It will be appreciated that for purposes of clarity and where deemed appropriate, reference numerals have been repeated in the figures to indicate corresponding features, and that the various elements in the drawings have not necessarily been drawn to scale in order to better show the features.

DETAILED DESCRIPTION

FIG. 1 illustrates one embodiment of a cardiac retractor 20. The retractor has a fixed collar 22 which is fixedly attached to the proximal end 24P of an outer tube 24. A fixed link 26 is fixedly attached to the distal end 24D of the outer tube 24. A coaxial nut 28 is coupled to a keyed link 30 by elements which are not visible in this view, but which will be shown and discussed later in this specification. The coaxial nut 28 is coupled to a fixed key (not visible in this view) which can be rotated around an axis 32 of the outer tube 24 to cause a related movement of the keyed link 30. As shown in FIG. 1, the with the coaxial nut 28 aligned over the fixed collar 22, the keyed link 30 is opened or deployed relative to the fixed link 26.

In this embodiment, the cardiac retractor 20 has a series of additional links in addition to the fixed link 26 and the keyed link 30. Two opposing links 34 are located opposite the keyed link 30 and the fixed link 26. The opposing links 34 are coupled together by a coupling link 36. A first opposing link 34 is coupled to the fixed link 26 by two side links 38, while a second opposing link 34 is coupled to the keyed link 30 by two side links 40. Each link in a pair of adjacent links (30/40, 40/40, 40/34, 34/36, 36/34, 34/38, 38/26) is pivotable relative to each other. A deployment cable 42 is routed around the links 26, 38, 38, 34, 36, 34, 40, 40, 30 in a pattern which will cause the links to open into the deployed state shown in FIG. 1 when tension is applied to the deployment cable 42 by a cable tension screw knob 44.

FIGS. 2A-2H and 2J are a series of exploded perspective views which illustrate the partial assembly of the cardiac retractor of FIG. 1. It should be noted that there is intentionally not a FIG. 2I to avoid confusion with the number 21. As shown in FIG. 2A, the outer tube 24 is coupled to the fixed link 26 at the distal end 24D of the outer tube 24. The proximal end 24P of the outer tube 24 is coupled to the fixed collar at a distal side 46D of a passthrough hole 46 in the fixed collar 22.

As shown in FIG. 2B, a cable bushing 48 is coupled to the keyed link 30. The keyed link 30 has a keyed opening 50 to which reference will be made in a later figure. As shown in FIG. 2C, hinges 52 of the opposing links 34 are aligned with corresponding hinges 54 of the coupling link 36. Similarly, hinge 56 of one of the side links 38 is aligned with corresponding hinge 58 of the first opposing link 34, while hinge 60 of one of the side links 40 is aligned with corresponding hinge 62 of the second opposing link 34. Also similarly, hinge 64 of another of the side links 38 is aligned with hinge 66 of the other side link 38, while hinge 68 of another of the side links 40 is aligned with the hinge 70 of the other side link 40. A series of side rollers 72 is aligned with a hinge on each of the links 38, 40, 34. The side rollers 72 line up with cable guide slots 74 in the links. As shown in FIG. 2D, a series of hinge pins 76 is used to hold each of the hinged joints between links 38, 40, 34 together, including the side rollers 72.

As shown in FIG. 2E, a hinge 78 of the keyed link 30 is brought into alignment with a hinge 80 of the fixed link 26. A hinge 82 of the side link 40 on one end is aligned with a hinge 84 of the keyed link 30. Similarly, a hinge 86 of the side link 38 on another end is aligned with a hinge 88 of the fixed link 26. As shown in FIG. 2F, the keyed link 30 is held pivotably coupled to the fixed link 26 by a threaded axle 90 which passed through the end of the keyed link 30 and screws into the fixed link 26. Hinge pins 92 are used to pivotably couple the keyed link 30 and fixed link 26 to their respective side links 40, 38.

As shown in FIG. 2G, a tube drive 94 having a keyed end 96 is coupled to the distal end 98D of an inner tube 98. The assembled tube drive 94 and inner tube 98 are then inserted into the proximal side opening 46P of a passthrough hole 46 in the fixed collar 22 until the keyed end 96 of the tube drive 94 engages the keyed opening 50 (visible in FIG. 2B) of the keyed link 30.

As shown in FIG. 2H, a deployment cable 100 is added to the cardiac retractor 20. The deployment cable 100 is routed around the links 26, 38, 38, 34, 36, 34, 40, 40, 30 as shown in the side view of FIG. 2K. FIG. 2J is an enlarged view of a portion of FIG. 2H, which shows an opening 102 in the cable bushing 48. After routing the deployment cable 100 around the links as shown in FIG. 2K, the ends of the deployment cable 100 are passed through the opening 102 in the cable bushing 48, passed down through the inner tube 98 (previously visible in FIG. 2G), and out of the opening 46P in the fixed collar 22 (also previously visible in FIG. 2G).

The ends 100E if the deployment cable 100 are shown exiting the opening 46P in FIG. 2L. An assembly spacer 104 (also known as a cable tube) is placed over the deployment cable ends 100E and into the opening 46P and slide inside the inner tube 98 (previously visible in FIG. 2G). A tension nut 106 is also placed over the deployment cable ends 100E and into the opening 46P to slide against the assembly spacer 104. A cable lock wedge 108 is pressed into the proximal end 106P of the tension nut 106, pinning the deployment cable 100 within the tension nut 106 while forcing the deployment cable ends 100E into slots 110 in the tension nut 106. Excess cable ends 100E are then trimmed at the tension nut 106. A threaded rod 112 is then threaded into the tension nut 106.

As shown in FIG. 2M, the proximal end 112P of threaded rod 112 protrudes from the fixed collar 22. A key mount collar 114 is passed over the proximal end 112P of threaded rod 112 and coupled to the inner tube 98 (previously visible in FIG. 2G). In the view of FIG. 2M, we also call out the attachment hole 114A and the groove 114G of key mount collar 114, since both will be referred to in the following figure. The cable tension screw knob 44 is then placed over the proximal end 114P of the key mount collar 114 while also being fixedly coupled to the proximal end 112P of threaded rod 112.

As shown in FIG. 2N, a set screw 116 is threaded into hole 44H of the cable tension screw knob 44 so that the set screw 116 also rides in the groove 114G of the key mount collar 114 (previously visible in FIG. 2M). A fixed key 118 is passed through the fixed collar 22 and coupled to the attachment hole 114A of the key mount collar 114. The coaxial nut 28 is slid over the fixed key 118, while a retaining washer 120 is coupled to the end of the fixed key 118 in order to keep the coaxial nut 28 from coming off the fixed key 118. The fixed collar 22 has a slot 122 which is sized to allow the fixed key 118 to be rotated out of the fixed collar 22 when the coaxial nut 28 is not threaded onto the fixed collar 22. Rotating the fixed key 118, rotates the key mount collar 114 to which it is connected, which in turn rotates the inner tube 98 (previously visible in FIG. 2G) to which it is connected, which in turn rotates the tube drive 94, which in turn rotates the keyed link 30 to which it is connected. When the fixed key 118 is aligned with the fixed collar 22, the keyed link 30 is in the open or deployed position shown in FIG. 2N. When the fixed key 118 is rotated out of the fixed collar 22, the keyed link 30 pivots towards the fixed link 26 for a closed or undeployed position (not shown in this view).

FIG. 3A is a top view of the cardiac retractor 20 of FIG. 1 showing cross-section line 3B-3B. FIG. 3B is a side cross-sectional view of the cardiac retractor 20 of FIG. 3A.

FIG. 4 is a distal perspective view of one embodiment of a keyhole cannula 124 for use with a cardiac retractor 20 such as the retractor of FIG. 1. The keyhole cannula 124 has an instrument passage 126 which in this embodiment is oblong in shape. Coupled to the instrument passage 126 is a key hole 128 which is sized to accept the outer tube 24 of the cardiac retractor 20 such that the device may only be slid into the key hole 128 along a key hole axis 130 which is substantially perpendicular to the opening of the passage 126. To accomplish this, the key hole 128 covers an arc of more than 180 degrees, thereby preventing a tube large enough to fill the whole key hole 128 from leaving the key hole 128 unless withdrawn axially. In other embodiments, the key hole axis might not be substantially perpendicular to the opening of the passage, however, the fixed alignment between the key hole axis 130 and the cannula 124 means that the cannula will always be facing a known direction relative to an instrument being placed into the key hole 128, thereby helping to ensure that the cannula is aligned with the instrument being placed therein and engaging the key hole 128. This can help facilitate visualization for the surgeon through the cannula to the point where work is being done inside the patient. In this embodiment, the cannula 124 also has some ribbing 132 and is sized to fit within an intercostal space of a patient's rib cage.

FIGS. 5A, 5B, 5C, 5D, 5E, and 5F are front, left, right, back, top, and bottom views, respectively, of the keyhole cannula 124 of FIG. 4.

FIGS. 6A-6H, 6J-6N, and 6P-6R illustrate an example of a surgical procedure using the cardiac retractor of FIG. 1 and the keyhole cannula of FIG. 4. FIG. 6A illustrates a patient 134 with a portion of their ribcage 136 visible, and their heart 138 within the thoracic cavity. As shown in FIG. 6B, an incision 140 is made in an intercostal space 142 of the ribcage 136. As shown in FIG. 6C, a keyhole cannula 124 may be placed within the intercostal incision 140. The long outer sides of the cannula 124 are smooth and do not have ribbing in order to avoid traumatizing nerves and vessels which may run along the adjacent ribs. FIG. 6D is an enlarged schematic view of the heart 138, such as a surgeon might see when looking through the cannula 124. As shown in FIG. 6E, vessels 144 may be manipulated to locate a desired incision point 146 on the wall of the heart 138. As shown in FIG. 6F, an incision 148 may be made in the wall of the heart 138 at the desired location. In this example, the incision 148 has been made into the left atrium of the heart 138.

FIG. 6G refocuses on the outside of the patient. The cardiac retractor 20 having its fixed key 118 is rotated out of the fixed collar 22 so that the keyed link 30 is rotated down towards the fixed link 26, and with the other links folded therebetween because tension has not been applied to the deployment cable 100 by the tension knob 44 is inserted into the key hole 128 of the keyhole cannula 124. The folded links 26, 30 fit within the cannula passage 126, while the key hole 128 is sized to hold the outer tube 24. Once the links have passed through the cannula, the outer tube 24 can be rotated within the cannula 124 to orient the folded links as desired. As shown in FIG. 6H, looking back at the heart 138 again, the folded links have been rotated to align with the incision 148. This is shown in a schematic elevational view of FIG. 6J, where the folded links 26, 38, 38, 34, 36, 34, 40, 40, and 30 can be seen in a closed or undeployed configuration. For simplicity, the deployment cable is not shown in this view.

As shown in FIG. 6K, outside the patient again, the fixed key 118 is then rotated into alignment with the fixed collar 22, and then, as shown in FIG. 6L, the coaxial nut 28 is threaded into onto threads within the fixed collar 22 to hold the fixed key 118 in this deployed position. Inside the patient, this rotation of the fixed key 118 into alignment with the fixed collar 22 results in the keyed link 30 pivoting to the open/deployed position relative to the fixed link 26 as shown in the perspective view of FIG. 6M and the schematic elevational view of FIG. 6N.

FIG. 6P refocuses outside the patient again. The tension knob 44 is tightened, drawing the tension nut 106 proximally towards the user, and applying tension to the deployment cable 100. This causes the links 38, 38, 34, 36, 36, 40, and 40 to create an opening 150, visible in the inside-patient-views of FIGS. 6Q and 6R, which effectively retracts the wall of the heart, allowing for surgical access. For simplicity, the deployment suture is not shown in FIG. 6Q, however, the tensioned deployment cable is shown schematically in FIG. 6R.

FIG. 7 is a perspective view of another embodiment of a cardiac retractor 152. This embodiment is similar to the previous embodiment, except that the tension knob 154 is coupled to the deployment cable 156 in a different manner. FIG. 8A is a top view of the cardiac retractor 152 of FIG. 7 showing cross-section line 8B-8B. In this view, it can be seen that the ends 156E of the deployment cable 156 are coupled directly to a tension rod 158 which passes within the fixed and keyed links 26, 30. The tension rod 158 is directly coupled to the tension knob 154 such that rotation of the tension knob 154 rotates the tension rod 158, thereby either drawing in or letting out the deployment cable 156. FIG. 8B is a side cross-sectional view of the cardiac retractor of FIG. 8A, taken along line 8B-8B.

FIGS. 9A and 9B are both partial cross-sectional and partially exposed views which illustrate the deployment cable mechanism for the cardiac retractor embodiment of FIG. 7. In FIG. 9A, the tension knob 154 has been loosed, meaning the folded links are not caused to be deployed. In FIG. 9B, the tension knob has been tightened, causing the deployment cable 156 to wrap around the tension rod 158, thereby causing the deployment cable 156 to open the links 38, 38, 34, 36, 34, 40, and 40.

FIG. 10 is a perspective view of a distal end of another embodiment of a cardiac retractor. This embodiment of a distal end 160 of another embodiment of a cardiac retractor is fabricated using a single piece of material, most likely plastic. Other embodiments may use other materials capable of being formed in such a monolithic manner of a single piece having similar features as the embodiment described herein, for example, a variety of plastics, metals, elastomers, or combinations thereof. Alternate embodiments may include more than one single piece and be joined in a similar manner as embodiments described previously herein. The distal end 160 defines all features illustrated in FIG. 10, as it is of a singular piece. The distal end 160 defines a fixed collar 165 coupled to an outer tube 162, and a fixed top panel 168 also fixedly coupled to the outer tube 162. A keyed top panel 166 is also coupled to the outer tube 162, the keyed top panel 166 and the fixed top panel 168 along with the collar 165 forming a barrel hinge 164. The keyed top panel 166 is coupled to a side panel 170 by a living hinge 182, a second side panel 172 is coupled to side panel 170 by a living hinge 184, a bottom panel 174 is coupled to the side panel 172 by a living hinge 186, a second bottom panel 176 is coupled to the bottom panel 174 by a living hinge 188, a third side panel 178 is coupled to the second bottom panel 176 by a living hinge 190, a fourth side panel 180 is coupled to the third side panel 178 by a living hinge 192, and the fourth side panel 180 is coupled to the fixed top panel 168 by a living hinge 194, which is not visible here. The various living hinges 182, 184, 186, 188, 190, 192, 194 allow the various panels 166, 168, 170, 172, 174, 176, 178, 180 to fold into various stages of deployment as illustrated with previous embodiments of cardiac retractor described and depicted herein.

FIGS. 11A-11C are schematic elevational views of the distal end of the cardiac retractor of FIG. 10 illustrating various states of deployment of the cardiac retractor. These various stages of deployment are shown outside of an anatomical location, as compared to previously described embodiments for the purpose of clarity. FIG. 11A shows the cardiac retractor having its fixed key 200 rotated outward and having shaft 196 also in an outward position such that the fixed top panel 168 is rotated down towards the keyed top panel 166, and with the other links folded therebetween. The folded panels would fit within a cannula passage as previously shown, while the key hole is sized to hold the outer tube 162. Once the links have passed through the cannula, the outer tube 162 can be rotated within the cannula to orient the folded links as desired.

As shown in FIG. 11B, the fixed key 200 is then rotated in direction 206 into alignment with the fixed collar 198, and then, the coaxial nut 202 is threaded into onto threads 204 at the end of shaft 196 to hold the fixed key 200 in this partially deployed position. Once inside the patient (not shown here), this rotation of the fixed key 200 into alignment with the fixed collar 198 results in the keyed top panel 166 pivoting to the partially open/partially deployed position relative to the fixed top panel 168 as shown in FIG. 11B. A fully deployed position as illustrated in FIG. 11C can be achieved by manual manipulation by a surgeon, utilizing a grasper, a tenaculum or other surgical tools known to those skilled in the arts.

FIGS. 12A-12B are schematic elevational views of the distal end of another embodiment of a cardiac retractor, this embodiment having additional internal support arms. In the embodiment shown in FIGS. 12A and 12B, similar features described in regard to FIG. 10 are illustrated, but most of the side panels are removed from this view to focus on several support arms. The distal end of the cardiac retractor shown in FIG. 12A defines a barrel hinge 208, a top fixed panel 212, and a top keyed panel 210. A side panel 226 is coupled to the top keyed panel 210 and a side panel 224 is coupled to the top fixed panel 212. Coupled between the side panel 224 and top fixed panel 212 and coupled between the side panel 226 and top keyed panel 210, is a first support arm segment 218 coupled to a living support arm hinge 220 coupled to a second support arm segment 222. Each of the first support arm segments 218 are coupled directly to both top panels 210, 212 by a hinge pin 216 at the end of each first support arm segment 218 being snapped into a hinge knuckle 214 defined by each of the top panels 210, 212. FIG. 12B illustrates the distal end of the cardiac retractor in a fully deployed state. The support arms and their respective components, the first support arm segment 218, support arm hinge 220, and second support arm segment 222 are shown in a deployed and extended state. The function of the support arms is to provide support to between each top panel 210, 212 and each side panel 226, 224 until such time as a procedure requiring the use of a cardiac retractor is completed. The cardiac retractor may then be folded into a closed position and removed from the surgical site.

Various advantages of a cardiac retractor have been discussed above. Embodiments discussed herein have been described by way of example in this specification. It will be apparent to those skilled in the art that the forgoing detailed disclosure is intended to be presented by way of example only, and is not limiting. Various alterations, improvements, and modifications will occur and are intended to those skilled in the art, though not expressly stated herein. These alterations, improvements, and modifications are intended to be suggested hereby, and are within the spirit and the scope of the claimed invention. Additionally, the recited order of processing elements or sequences, or the use of numbers, letters, or other designations therefore, is not intended to limit the claims to any order, except as may be specified in the claims. Accordingly, the invention is limited only by the following claims and equivalents thereto. 

What is claimed is:
 1. A cardiac retractor, comprising: an outer tube that extends along a longitudinal axis from a proximal end to a distal end; a fixed top panel fixedly coupled to the distal end of the outer tube; a keyed top panel rotatably coupled to the distal end of the outer tube such that the keyed top panel rotates relative to the fixed top panel between an undeployed position and a deployed position.
 2. The cardiac retractor of claim 1, further comprising an inner tube disposed within a portion of the outer tube such that the inner tube extends along the longitudinal axis from a proximal end to a distal end, wherein the inner tube is configured to rotate relative to the outer tube about the longitudinal axis, and wherein the keyed top panel is fixedly coupled to the distal end of the inner tube such that rotation of the inner tube relative to the outer tube rotates the keyed top panel relative to the fixed top panel between the undeployed position and the deployed position.
 3. The cardiac retractor of claim 1, wherein the keyed top panel is coupled to the distal end of the outer tube by a hinge such that the keyed top panel rotates relative to the fixed top panel about the hinge.
 4. The cardiac retractor of claim 1, wherein the fixed top panel is substantially planar and the keyed top panel is substantially planar.
 5. The cardiac retractor of claim 1, further comprising: a first side panel pivotably coupled to the keyed top panel; a second side panel pivotably coupled to the first side panel; a first bottom panel pivotably coupled to the second side panel; a second bottom panel pivotably coupled to the first bottom panel; a third side panel pivotably coupled to the second bottom panel; and a fourth side panel pivotably coupled to the fixed top panel and to the third side panel.
 6. The cardiac retractor of claim 5, wherein: the first side panel is pivotably coupled to the keyed top panel by a first living hinge, the second side panel is pivotably coupled to the first side panel by a second living hinge, the first bottom panel is pivotably coupled to the second side panel by a third living hinge, the second bottom panel is pivotably coupled to the first bottom panel by a fourth living hinge, the third side panel is pivotably coupled to the second bottom panel by a fifth living hinge; the fourth side panel is pivotably coupled to the third side panel by a sixth living hinge, and the fourth side panel is pivotably coupled to the fixed top panel by a seventh living hinge.
 7. The cardiac retractor of claim 5, wherein the first side panel, the second side panel, the first bottom panel, the second bottom panel, the third side panel, and the fourth side panel are each substantially planar.
 8. The cardiac retractor of claim 7, wherein in the deployed position, an inner surface of the keyed top panel faces an inner surface of the first bottom panel and an inner surface of the fixed top panel faces an inner surface of second bottom panel.
 9. The cardiac retractor of claim 8, wherein in the deployed position, an inner surface of the first side panel faces an inner surface of the fourth side panel and an inner surface of the second side panel faces an inner surface of the third side panel.
 10. The cardiac retractor of claim 9, wherein in the deployed position, the inner surface of the second side panel is substantially normal to the inner surface of the first bottom panel and the inner surface of the third side panel is substantially normal to the inner surface of the second bottom panel.
 11. The cardiac retractor of claim 7, wherein in the undeployed position, an inner surface of the keyed top panel faces an inner surface of the first side panel and an inner surface of the fixed top panel faces an inner surface of the fourth side panel.
 12. The cardiac retractor of claim 11, wherein in the undeployed position, an outer surface of the first side panel faces an outer surface of the second side panel and an outer surface of the third side panel faces an outer surface of the fourth side panel.
 13. The cardiac retractor of claim 7, wherein in the undeployed position, the first bottom panel and the second bottom panel are disposed between an inner surface of the fixed top panel and an inner surface of the keyed top panel.
 14. The cardiac retractor of claim 5, wherein the keyed top panel is pivotably coupled to the outer tube along a first longitudinal edge of the keyed top panel, and the keyed top panel is pivotably coupled to the first side panel along a second longitudinal edge of the keyed top panel, wherein the first longitudinal edge of the keyed top panel is opposite to the second longitudinal edge of the keyed top panel.
 15. The cardiac retractor of claim 14, wherein a first longitudinal edge of the fixed top panel is disposed adjacent to the outer tube and a second longitudinal axis of the fixed top panel is pivotably coupled to the fourth side panel, wherein the first longitudinal edge of the fixed top panel is opposite to the second longitudinal edge of the fixed top panel.
 16. The cardiac retractor of claim 5, wherein the keyed top panel, the fixed top panel, the first side panel, the second side panel, the first bottom panel, the second bottom panel, the third side panel, and the fourth side panel are a single, unitary part that is coupled to the outer tube.
 17. The cardiac retractor of claim 5, further comprising a first support arm assembly, the first support arm assembly comprising: a first support arm segment having a first end coupled to a portion of the fixed top panel; a second support arm segment having a first end coupled to a portion of the fourth side panel; and a support arm hinge, wherein a second end of the first support arm segment is coupled to a first portion of the support arm hinge and a second end of the second support arm segment is coupled to a second portion of the support arm hinge.
 18. The cardiac retractor of claim 17, wherein the first end of the first support arm segment is coupled to the portion of the fixed top panel by a hinge pin that is received into a hinge knuckle.
 19. The cardiac retractor of claim 18, wherein the hinge pin is coupled to the first end of the first support arm segment and the hinge knuckle is disposed at the portion of the fixed top panel.
 20. The cardiac retractor of claim 19, wherein the support arm hinge is a living hinge, and wherein the first support arm segment, the support arm hinge, the second support arm segment, and the hinge pin for a single, unitary part. 